1. Field of the Invention
The present invention relates to improvement of a quantity-of-light adjusting device for adjusting passing light flux by opening and closing an opening with multiple quantity-of-light adjusting blades, and an exposure adjusting device for a camera.
2. Description of the Related Art
Hitherto, various types of devices having iris blades or shutter blades or the like for adjusting the quantity of light so that the exposure on a recording medium such as film or a CCD is a suitable level have been proposed, and many proposals have been made regarding the method for detecting the position (turning state) of the iris blades or shutter blades.
For example, with a known shutter device wherein light flux for photography is shielded or passed by turning of two shutter blades, a slit shape is provided near the tip of one of the two shutter blades, and the slit shape is passed over a sensor such as a photo-interrupter or the like, thereby detecting the position of the shutter blade, which is used for controlling exposure.
Also, Japanese Patent Laid-Open No. 2001-042382 discloses an arrangement configured of two sets of shutter blades, each set formed of two blades, and each set turning in opposite directions, wherein a slit shape is provided at the tips of the two shutter blades turning in the same direction with different rotating angles for the two shutter blades, so that signals at the time of the blades beginning to open can be detected multiple times, to be used for determining whether or not exposure trouble has occurred.
Further, Japanese Patent No. 2,627,168 and Japanese Patent No. 2,909,629 propose detecting an external shape edge face of one shutter blade with a photo-sensor or the like.
However, attempting to detect the position of a shutter blade with a slit shape formed on one shutter blade as described above results in detection of the shutter being limited to an extremely limited range where the shutter blade begins to move, and in the event that the shutter blade is to be detected from the beginning of motion to the fully-open position, either multiple slit shapes must be formed or multiple detecting means must be provided, resulting in increased size of the shutter blades, which in turn increases the size of the shutter device, increases costs, and so forth.
With the exposure adjusting device disclosed in Japanese Patent Laid-Open No. 2001-042382, only signals near where the shutter blade begins to move can be obtained, and attempting to detect the position of the blade from the beginning of motion to the fully-open position increases the size of the shutter blades, which increases the size of the shutter device and increases costs.
Also, with the exposure adjusting device disclosed in Japanese Patent Laid-Open No. 06-281995, there is no need to provide special shapes such as slits or the like to the shutter blades, so the device does not become oversized, but there is the need to subject the shutter blades to magnetic electroplating, and the further magnetization, which inevitably leads to increased costs.